While most of us can’t taste colors or see sounds, some people can actually taste the rainbow and see musical notes they hear. Imagine seeing the color purple and experiencing a sweet taste in your mouth, or hearing a note played on the piano and seeing the color blue. This relatively unknown condition is called synesthesia, which is the blending of senses. More specifically, it is a sensory phenomenon where the stimulation of one sense prompts the activation of another sense without directly stimulating it.
For example, one may hear something such as music, or even another person’s voice and see or associate that sound with a color. This type of synesthesia is known as chromesthesia. Experiencing a taste with a certain color is known as flavor-color synesthesia. Another type of synesthesia is grapheme-color synesthesia in which letters and numbers are associated with colors. Although there are a wide variety of synesthetic experiences, chromesthesia and grapheme-color synesthesia are among the most common.
Synesthesia is a complex condition, and research on this topic is still working to gain momentum. Our understanding of the brain is limited, and so far, scientists have been unable to pinpoint the cause or underlying mechanisms of this condition. They have, however, come up with many different hypotheses.
While research on synesthesia is still in its budding phase, there are four proposed models. Cross-activation theorizes that there are connections that don’t disappear after childhood and instead continue into adulthood. This involves the activity of adjacent areas of the brain, such as the V4 area (part of the brain that processes visual information) and the area for recognizing letters and numbers right next to it. Long-range disinhibited feedback theory contradicts this theory of abnormal connections. Instead, it states that synesthetic experiences are a result of normal neural connections that all humans have. Re-entrant processing involves visual information being transferred from lower to higher level areas in the brain, where it’s analyzed before being transferred back to lower levels so it can be analyzed again. This processing plays a huge rule in perception and visual awareness. The last theory is hyperbinding. The human brain has to combine all sorts of information to make sense of the world, and hyperbinding suggests synesthesia is a result of overactive binding. Although there are these proposed models, study results show that synesthetic experiences are a result of an entire network of areas in the brain.
This then leads to the idea that synesthesia involves not only the areas of the brain responsible for the senses, but also the association area, which makes connections and processes different information at the same time. In one investigation, MRI’s of the brains of people with grapheme-color synesthesia were taken. The results showed that the visual area of the brain was active even without visual stimulation, so there may be a link between the association area of the brain and the primary visual area.
In contrast, two scientists focused more on how synesthesia might be acquired rather than how it worked. In 2013, scientists Witthoft and Winawer found a dozen people with grapheme-color synesthesia whose letter-color pairings deviated from the norm. Instead of “R” and “Y” being associated with the colors red and yellow, these twelve people associated the two letters with purple and red respectively. It turns out these letter-color pairings matched magnetic letters sold by Fisher-Price, and the majority of the synesthetes (those who have synesthesia), had those magnetic letters as children.
Of course, most people with grapheme-color synesthesia didn’t acquire their associations from Fisher-Price letters. This is an example of an unreliable study; the sample size is extremely small, and the results can’t be applied to other people with synesthesia due to the complexity of the condition. While synesthesia may or may not be acquirable, this study is a reminder that memory and learning might be important parts of synesthesia research.
However, synesthesia must be something more than just childhood memories or learned associations. In the case of a colorblind synesthete, he reported seeing “Martian colors”, which means he was seeing colors he was incapable of seeing due to his colorblindness. Interestingly, many synesthetes comment on how the colors they see are “ugly”. If synesthesia weren’t an automatic response, then the only other option is the synesthetes are consciously able to choose the colors they see. But why would they choose an ugly color?
This is a particularly tricky area of study in terms of reliability and methodology, as many studies rely on self-reporting from the synesthete themselves. There are also so many different types and expressions of synesthesia that it’s difficult to apply study results to synesthesia in general.
The lack of research means that there are still many misunderstandings about this condition. Even though synesthesia is a neurological condition, it generally doesn’t cause any discomfort or trouble in day to day life. Synesthesia is merely a difference in perception and is not the same as mental imagery. Brain scans show that brain activity in synesthetes is similar to the brain activity of someone actually perceiving the color, and is different from the brain patterns of someone who is merely imagining something. Another common misconception is that synesthetes see detailed, elaborate pictures. This is not the case; instead, they see simple things like moving colors that appear and disappear.
Perhaps in the future there may be concrete answers, but for now, the cause of synesthesia remains elusive. If we’re able to figure out what the underlying mechanisms are, this could lead to a greater understanding of brain function with regard to perception and cognition. And while scientists work to uncover the secret behind this condition, we should work toward a greater understanding of this condition. People are different, and just like no two people have the same fingerprints, we all have different perceptions of the world, especially those who are synesthetic. In fact, many synesthetes enjoy what they have, despite how distracting it can be. I mean, who wouldn’t love to experience senses in a totally different way?
by: B. Sun
References
Jean-Pierre Ternaux. “Synesthesia: A Multimodal Combination of Senses.” Leonardo, vol. 36, no. 4, 2003, pp. 321–322. JSTOR, JSTOR, www.jstor.org/stable/1577334
Witthoft, N. and Winawer, J., “News from the Field , Attention, Perception, & Psychophysics.” DeepDyve, Springer Journals, vol. 75, no. 4, 17 Apr. 2013, www.deepdyve.com/lp/springer-journals/news-from-the-field-H71oMefby0
Cytowic, Richard E., et al. Wednesday Is Indigo Blue : Discovering the Brain of Synesthesia, “Chapter 1: What Color Is Tuesday?” MIT Press, 2009. ProQuest Ebook Central, https://ebookcentral-proquest-com.libproxy.lib.unc.edu/lib/unc/detail.action?docID=3338997
Hubbard, Edward M. “Neurophysiology of Synesthesia.” SpringerLink, Current Science Inc., 3 July 2007, link.springer.com/article/10.1007%2Fs11920-007-0018-6
Mylopoulos, Myrto I., and Tony Ro. “Synesthesia: a Colorful Word with a Touching Sound?” Frontiers, Frontiers, 29 Sept. 2013, journal.frontiersin.org/article/10.3389/fpsyg.2013.00763/full